There are many and various types of falling film condensing heat exchangers, hereinafter referred to as condensers. Wide variations in the heat exchange performance of these condensers can be attributed, at least in part, to incomplete, non-uniform and unstable formation of a liquid film about the tubes containing the coolant. That is, the external surfaces of every tube containing the coolant does not have a continuous, uniform coating of liquid film on the shell side along its entire length. Rather, those surfaces at the upper (vapor inlet) end of the heat exchanger and immediately below each support plate are exposed directly to the vapor being condensed, resulting in poor heat transfer capacity. Liquid, of course, conducts heat better than a vapor. Consequently, the lack of a continuous top to bottom thin film of liquid about the coolant carrying tubes within the condenser precludes effective realization of high, theoretically possible overall heat transfer coefficients which would otherwise enable a substantial reduction in heat exchange surface area for a given condensing duty. A direct result of this failure is the necessity to provide large heat transfer areas (the coolant/vapor interface) which substantially increases the cost of a condenser for a given condensing duty. In short, the problem associated with prior falling film condensing heat exchangers is the failure to establish a uniform liquid film on the coolant carrying condensing tubes as the vapor phase condenses about the tubes, especially at the vapor inlet end of the tubes and the maintenance of this film as the tubes pass through support plates located axially along their length.